/Engine/Source/Editor/UnrealEd/Public/EditorModeRegistry.h
Allows mode factories to handle selection change events, and potentially activate/deactivate modes
virtual void OnSelectionChanged ( [FEditorModeTools](API\Editor\UnrealEd\FEditorModeTools) & Tools, [UObject](API\Runtime\CoreUObject\UObject\UObject) * ItemUndergoingChange ) const